Final answer:
The pH of the buffer composed of equimolar amounts of C5H5NHCl and C5H5N can be found using the Henderson-Hasselbalch equation and approximates to the pKa of the conjugate acid of C5H5N. To determine the exact pH, the Kb value of C5H5N is necessary, which is missing in the question. Once the Kb is known, the pKa can be calculated and thus the pH, as pH equals pKa in equimolar buffer solutions.
Step-by-step explanation:
The pH of a buffer solution composed of C5H5NHCl (a salt form which will provide the conjugate acid C5H5NH+) and C5H5N (a weak base, pyridine) can be calculated using the Henderson-Hasselbalch equation. Given that the amounts of weak base and its conjugate acid are equimolar, the pH will be approximately equal to the pKa of the conjugate acid of the base. The pKa value can be calculated from the provided Kb value of C5H5N using the relationship pKa + pKb = pKw, where pKw is 14 at 25°C. The Henderson-Hasselbalch equation is pH = pKa + log([base]/[acid]), which simplifies to pH = pKa when the concentrations of acid and base are equal.
Unfortunately, the Kb value for C5H5N is not provided in the question. However, if it were known, you could calculate pKa as follows:
- Calculate pKb: pKb = -log(Kb).
- Determine pKa: pKa = 14 - pKb (at 25°C).
- Calculate pH: pH = pKa (for equal concentrations of acid and base).
Thus, the pH of the buffer would be approximately equal to the pKa of the conjugate acid formed by C5H5NH+.